The human heart is divided into four compartments or chambers. The left and right atria are located in the upper portion of the heart and the left and right ventricles are located in the lower portion of the heart. The left and right atria are separated from each other by a muscular wall, the interatrial septum, while the ventricles are separated by the interventricular septum.
Either congenitally or by acquisition, abnormal openings, holes, or shunts can occur between the chambers of the heart or the great vessels, causing blood to inappropriately flow there through. Such deformities are usually congenital and originate during fetal life when the heart forms from a folded tube into a four chambered, two-unit system. The septal deformities result from the incomplete formation of the septum, or muscular wall, between the chambers of the heart and can cause significant morbidity.
One such septal deformity or defect, a patent foramen ovale (PFO), is a persistent, one-way, usually tunnel shaped, flap-like opening in the wall between the right atrium and left atrium of the heart. Since left atrial pressure is normally higher than right atrial pressure, the flap typically stays closed. Under certain conditions, however, right atrial pressure exceeds left atrial pressure, creating the possibility for right to left shunting that can allow blood clots to enter the systemic circulation. This is particularly problematic for patients who are prone to forming venous thrombi, such as those with deep vein thrombosis or clotting abnormalities. Patients with a PFO may be prone to a cerebrovascular accident known as a stroke.
Moreover, certain patients are prone to atrial arrhythmias (i.e., abnormal heart rhythms which can cause the heart to pump less effectively). In a common such abnormality, atrial fibrillation, the two upper chambers of the heart (i.e., the left atria and the right atria), quiver instead of beating in coordination with other cardiac chambers. Because the atria do not beat and empty cleanly during atrial fibrillation, blood can stagnate on the walls and form clots that can then pass through the heart and into the brain, causing a stroke or a transient ischemic attack. These clots typically form in a cul-de-sac in the heart called the left atrial appendage due to its tendency to have low or stagnant flow.
Nonsurgical (i.e., percutaneous) tissue treatment and closure of a patent foramen ovale and similar cardiac openings, such as an atrial septal defect or a ventricular septal defect, as well as obliteration of a left atrial appendage, can be achieved using a variety of mechanical devices that are introduced via an artery into a large peripheral vessel, e.g., the femoral vein. These devices typically consist of a structural framework with a scaffold material attached thereto. Currently available devices, however, are often complex to manufacture, are inconsistent in performance, require a technically complex implantation procedure, lack anatomic conformability, and lead to complications (e.g., thrombus formation, chronic inflammation, residual leaks, perforations, device fractures, and conduction system disturbances).
Improved devices, systems, and related methods for treating cardiac tissue and/or closing cardiac openings, such as, for example, a patent foramen ovale, and for obliterating cardiac cul-de-sacs, such as, for example, a left atrial appendage, are therefore needed.